Glazing with a soldered connector

ABSTRACT

A glazing is disclosed comprising at least one ply of glass having an electrically conductive component on at least one surface, and an electrical connector electrically connected to the electrically conductive component through a soldered joint, the solder of the joint having a composition comprising 0.5 wt % or more indium, wherein the electrical connector comprises a nickel plated contact for contacting the solder. Also disclosed are solders having a composition comprising 14 to 75 wt % In, 14 to 75 wt % Sn, to 5 wt % Ag, to 5 wt % Ni, and less than 0.1 wt % Pb. Also disclosed is use of a solder having a composition comprising 0.5 wt % or more indium to solder a nickel plated electrical connector to an electrically conductive component on the surface of a ply of glass. The aspects of the invention improve the durability of electrical connections on glazing.

The present invention relates to glazings and more particularly glazingscomprising soldered electrical connections between electricallyconductive components on surfaces of the glazings and electricalconnectors. The invention also relates to electrical connectors for usein such glazings and to solders to solder connectors to electricallyconductive components on the surface of glazings.

Glazings, especially vehicle glazings, may have electrically conductivecomponents, such as circuits printed on the surface of a ply of glass oran array of wires fixed within a laminated glazing, in electricalconnection to the wiring harness of a building or, more usually, avehicle. Such circuits find use as heating circuits, to promotede-misting or de-icing, or as antenna circuits. Generally, electricalconnection is made by a connector being soldered to an electricallyconductive substrate known as a bus bar, which may be provided directlyon the surface of a piece of glass, or fully or partly on a fired,printed band on the glass, known as an obscuration band. The bus bar istypically printed using a silver-containing ink. Historically, thesolder used to join the bus bar and the connector contained lead.However, lead is known to be harmful, and there is increasinglegislative pressure to use lead-free solders in industry.

Lead-free solders have been disclosed in, for example, WO-A-2004/068643which relates to tin-based solders (up to 90% by weight tin) comprisinga mechanical stress modifier selected from bismuth, indium or antimony.The solder may also contain silver and/or copper.

EP-2 177 305 discloses a lead-free solder alloy which can be used forsoldering vehicle mounted electronic circuits, the alloy consistsessentially of silver, indium (at 3 to 5.5 mass %), copper, optionallybismuth with the balance being tin.

WO-A-2007/110612 discloses some improved electrical connectors for usewith glazings. The structure of the connector is chosen to maximise theadhesion between the electrically conductive components in the glazingand is especially for use with lead-free solders.

WO-A-2007/021326 discloses a solder composition having a mixture ofelements including tin, indium, silver and bismuth and which includesbetween 30 to 85% tin and about 15 to 65% indium.

Unfortunately a number of lead-free solders can introduce problems whenused, in particular, in vehicle glazings because such solders are notgenerally intended for use on glazings and so are not tested byaccelerated aging for extended periods nor by extensive chemical testingusing aggressive chemicals. More particularly, accelerated durabilitytesting by the Applicants of indium containing solders used on glazingshas identified deterioration in performance especially at hightemperatures or in humidity exposure tests and thermal cycling tests.The consequence of this deterioration is a reduction in bond strengthbetween the solder and either the electrical connector or theelectrically conductive circuit printed on the surface of a ply ofglass. Although it is not yet clear what the mechanism is of suchdeterioration in bond strength, analysis has suggested that theformation of an intermetallic layer at the interface between the solderand the connector (especially when the connector is copper-containing)and also at the interface between the solder and the electricallyconductive circuit (especially when the circuit is printed using asilver-containing ink) may be responsible. Cracks seem to form at theseinterfaces after thermal and/or humidity cycling.

The intermetallic layer at the interface between the solder and theconnector is thought (at present) to result from a reaction betweencomponents of the solder (e.g. indium) and components of the connector(e.g. copper). The formation of intermetallic layers has been alsosuggested in Application Notes from the Indium Corporation of America(e.g. Indium/Copper Intermetallics).

It is an aim of the present invention to address the problems of theprior art and to provide a solution.

The present invention accordingly provides in a first aspect a glazingcomprising at least one ply of glass having an electrically conductivecomponent on at least one surface, and an electrical connectorelectrically connected to the electrically conductive component througha soldered joint, the solder of the joint having a compositioncomprising 0.5 wt % or more indium, wherein the electrical connectorcomprises a metal- (preferably nickel) plated contact for contacting thesolder.

Surprisingly, a nickel plated contact appears to reduce thedeterioration in bond strength upon thermal cycling, elevatedtemperature storage or humidity cycling. This is greatly advantageousbecause of the very extensive testing that electrical connections onvehicle glazings have to undergo to be accepted by vehicle manufacturersas well as the very high durability required in practice.

Preferably, the solder has a composition comprising 0.01 wt % or moreNi, preferably 0.01 wt % to 5 wt % Ni, more preferably 0.05 wt % to 5 wt% Ni. This is greatly advantageous because Ni containing solder appearsto further improve durability of the joint. It is not clear how thisoccurs, but it is, at present, thought by the applicants that thepresence of Ni in the solder has the effect of blocking any pores in theNi plating of the connector which, in particular after long termtesting, improves durability of the joint still further by reducingformulation of a connector-solder intermetallic layer through any poresin the Ni plating.

It is preferred if the solder comprises 0.06 wt % to 5 wt % Ni or 0.05to 2 wt % nickel, preferably 0.05 to 1 wt % nickel, more preferably 0.05to 0.5 wt % nickel and most preferably 0.08 to 0.2 wt % nickel.

Preferably, the solder comprises 0.1 to 2 wt % copper, more preferably0.1 wt % to 1 wt % copper. More preferred ranges of copper within thesolder comprise 0.2 wt % to 0.9 wt % and especially 0.2 wt % to 0.8 wt %copper.

Surprisingly, the presence of copper within the solder is thought toresult in improved bond strength especially after thermal cycling orhumidity/thermal testing. This is despite the fact that the presence ofcopper within the solder would be (prior to this invention) thought tolead to an increase in the formation of an intermetallic layer therebyincreasing such problems.

It is preferred that the solder has a composition comprising less than0.1 wt % Pb (i.e. is “Pb-free”). It is preferred that there is nodeliberate addition of Pb to the solder.

Solders according the invention may comprise 0.1 to 5 wt % silver,preferably 0.1 wt % or 0.5 wt % or more silver, more preferably 0.5 wt %to 2 wt % silver and most preferably 0.8 to 1.2 wt % silver.

Preferably, the solder has a composition comprising:

5 to 75 wt % In,

5 to 94 wt % Sn, and

0.1 to 5 wt % Ag.

It is preferred that the solder comprises 20 to 75 wt % indium, morepreferably 40 to 75 wt % indium and most preferably 60 to 75 wt %indium.

It is preferred that the solder comprises 20 to 60 wt % tin, morepreferably 20 to 40 wt % tin, 20 to 35 wt % tin, 25 to 35 wt % tin andmost preferably 27 to 32 wt % tin.

Surprisingly, it has been discovered that the presence of nickel in thesolder may be advantageous in relation to the thermal cycling/reductionin bond strength problem.

Consequently, in a second aspect, the present invention provides asolder having a composition comprising:

14 to 75 wt % In,

14 to 75 wt % Sn,

0.1 to 5 wt % Ag,

0.01 to 5 wt % Ni, and

less than 0.1 wt % Pb.

In relation to the second aspect it is preferred that the soldercomprises 20 to 75 wt % of indium, more preferably 40 to 75 wt % indiumand most preferably 60 to 75 wt % indium.

It is preferred that in the solder according to the second aspect, thesolder comprises 20 to 60 wt % tin, more preferably 20 to 40 wt % tin,20 to 35 wt % tin, 25 to 35 wt % tin and most preferably 27 to 32 wt %tin.

It is also preferred that the solder according to the second aspect ofthe invention comprises 0.06 wt % to 5 wt % Ni or 0.05 to 2 wt % nickel,preferably 0.05 to 1 wt % nickel, more preferably 0.05 to 0.5 wt %nickel and most preferably 0.08 to 0.2 wt % nickel.

Solders according to the second aspect of the invention preferablycomprise 0.2 to 2 wt % silver, more preferably 0.5 to 1.5 wt % silverand most preferably 0.8 to 1.2 wt % silver.

The solders according to the second aspect of the invention find use inproviding electrical connection between connectors and electricallyconductive circuits, especially circuits printed on the surface of a plyof glass.

Thus, preferably, in a third aspect the present invention provides useof a solder as claimed in any one of the preceding claims to solder anelectrical connector to an electrically conductive component on thesurface of a ply of glass.

In a fourth aspect the present invention provides a (preferably avehicle glazing) glazing comprising, at least one ply of glass having anelectrically conductive component on at least one surface, an electricalconnector soldered to the electrically conductive component,characterised in that the solder has a composition comprising:

14 to 75 wt % In,

14 to 75 wt % Sn,

0.1 to 5 wt % Ag, and

0.01 to 5 wt % Ni.

Preferred features of the solder of the second aspect of the inventionapply also to solders to be used in the glazings of the fourth aspect.

In glazings according to the present invention, it is preferred if theelectrically conductive component comprises electrically conductivesilver-containing ink. The conductive component will usually be acomponent which is printed using such silver containing ink onto thesurface of at least one ply of glass.

In a fifth aspect, the present invention provides an electricalconnector for electrical connection to an electrically conductivecomponent on the surface of a ply of glass through a soldered joint, thesolder of the joint having a composition comprising 0.5 wt % or moreindium, and wherein the electrical connector comprises a nickel platedcontact for contacting the solder.

In a sixth aspect, the present invention provides use of a solder havinga composition comprising 0.5 wt % or more indium to solder a nickelplated electrical connector to an electrically conductive component onthe surface of a ply of glass.

The present invention is illustrated by the examples.

EXAMPLE 1

In Example 1 solders according to the compositions described in Table 1were used to connect a busbar (silver frit) on the surface of a vehicleglazing glass ply with a copper-based connector having a bracket shape.The connector was either Ni plated or Sn plated. Solders 2 to 4 arecopper is containing solders. Solder 1 is a nickel containing solder.

The soldered joints to connectors were subjected to accelerated agingtests as follows:

Terminal bending (initial pull) in the X, Y and Z directions (where Zrefers to the direction perpendicular to the glass surface);

High temperature and humidity testing at 85° C., 95% relative humidityfor 100 hours;

Salt water spray (3 cycles);

Other chemical testing by immersion of the joint in the test chemical(liquid) for 2 hours. Test chemicals were: 0.1 N sulphuric acid, 0.1 Nsodium hydroxide, gasoline, gas oil/diesel fuel, kerosene, enginecoolant, and window washer liquid.

After testing the strength of the joint was determined by a controlledspeed pull perpendicular to glass surface (except X and Y bend tests).Peak force was measured. The results are described in Table 2, Table 3and Table 4 with strength reported in N.

TABLE 1 Component (in wt %) Solders In Sn Ag Ni Cu 1 70 28.9 1 0.1 — 270 28.8 1 — 0.2 3 70 28.5 1 — 0.5 4 70 28.2 1 — 0.8

TABLE 2 Test Initial Pull High Temp. & Humidity X Y Z (80° C., 95% RH,100 h) Ave. σ Ave. σ Ave. σ Ave. σ Solder 1 262.45 0.35 192.88 49.74189.28 13.19 182.10 5.09 (Sn Plating) Solder 1 294.17 4.77 219.95 0.35203.18 19.01 219.88 3.36 (Ni Plating) Solder 2 276.65 6.15 156.60 5.73190.60 17.49 191.82 25.70 (Sn Plating) Solder 2 317.15 30.48 265.42105.39 202.42 31.89 242.77 6.54 (Ni Plating) Solder 3 300.75 6.36 315.05119.85 218.36 21.23 207.03 15.87 (Sn Plating) Solder 3 297.05 14.42231.05 27.08 222.39 9.67 251.55 27.22 (Ni Plating) Solder 4 288.30 8.91221.85 3.75 193.02 10.97 190.43 16.51 (Sn Plating) Solder 4 280.90 0.56252.70 31.61 205.41 14.03 227.10 17.54 (Ni Plating) Solder 1: 70% In −28.9% Sn − 1% Ag − 0.1% Ni Solder 2: 70% In − 28.8% Sn − 1% Ag − 0.2% CuSolder 3: 70% In − 28.5% Sn − 1% Ag − 0.5% Cu Solder 4: 70% In − 28.2%Sn − 1% Ag − 0.8% Cu

TABLE 3 Test Corrosion Resistance (immersing for 2 h) Gas Oil/DieselEngine Window washer Solder and 0.1N H₂SO₄ 0.1N NaOH Gasoline FuelKerosene Coolant liquid Connector Ave. σ Ave. σ Ave. σ Ave. σ Ave. σAve. σ Ave. σ Solder 1 186.85 30.76 166.18 39.35 177.07 2.58 164.4513.44 191.43 9.72 176.08 11.70 191.23 17.36 (Sn Plating) Solder 1 191.854.45 180.78 11.28 193.15 7.57 201.05 2.12 210.67 14.81 170.23 5.13193.43 17.22 (Ni Plating) Solder 2 199.15 0.92 167.80 14.85 203.43 5.20204.00 4.38 202.18 24.29 206.13 5.83 216.85 5.30 (Sn Plating) Solder 2193.30 5.02 197.13 16.37 192.30 6.29 209.32 11.56 203.73 7.81 188.882.65 196.83 47.41 (Ni Plating) Solder 3 202.67 19.06 219.65 9.33 189.9810.22 220.68 23.44 210.58 24.71 206.75 0.07 210.18 1.87 (Sn Plating)Solder 3 206.65 3.32 226.58 5.27 238.45 9.62 199.28 9.30 205.33 13.12202.60 13.22 217.23 48.05 (Ni Plating) Solder 4 168.35 8.06 183.37 18.00178.18 2.58 182.93 4.42 178.98 5.27 167.40 2.83 208.65 46.24 (SnPlating) Solder 4 203.98 19.41 189.15 14.35 194.35 5.37 195.85 8.13183.80 6.43 192.35 3.04 226.53 5.55 (Ni Plating) Solder 1: 70% In −28.9% Sn − 1% Ag − 0.1% Ni Solder 2: 70% In − 28.8% Sn − 1% Ag − 0.2% CuSolder 3: 70% In − 28.5% Sn − 1% Ag − 0.5% Cu Solder 4: 70% In − 28.2%Sn − 1% Ag − 0.8% Cu

TABLE 4 Salt water spray (3 cycles) Solder and Connector Ave. σ Solder 1(Sn Plating) 182.37 17.29 Solder 1 (Ni Plating) 185.20 49.22 Solder 2(Sn Plating) 188.40 1.06 Solder 2 (Ni Plating) 230.03 5.55 Solder 3 (SnPlating) 209.95 27.22 Solder 3 (Ni Plating) 230.40 9.33 Solder 4 (SnPlating) 196.92 10.29 Solder 4 (Ni Plating) 210.07 5.76

As is apparent in Tables 2, 3 and 4, use of a Ni plated connectorresults in significant retention of strength in the joint even afterhigh temperature/high humidity test for 100 hours and after chemicalimmersion tests, in particular in alkali media.

EXAMPLE 2

In Example 2, a number of solders as described in Table 5 were used tojoin a connector as in Example 1 to a busbar on a glass surface. Thesoldered joints were subjected to tests as follows and the strength ofjoin determined as in Example 1:

Initial pull strength in Z direction;

500 thermal cycles (−30° C. 29 min to 20° C. 1 m to 80° C. 29 min to 20°C. 1 min).

High temperature (80° C.) and high humidity (95% relative humidity) for360 and 720 hours;

High temperature (100° C.) for 1000 hours;

Low temperature (−30° C.) for 1000 hours.

The results are reproduced for solders 5-7 with connectors with Snplating or Ni plating in Table 6 and Table 7. Also in Tables 6 and 7 areresults (Sn plating or Ni plating) for solders 1 to 4.

The use of Ni plated contacts significantly improves strength of joineven after extensive testing. The results are particularly significantafter high temperature testing for a prolonged period.

TABLE 5 Component (in wt %) Solders In Sn Ag Ni Cu 5 55 42.5 2.5 — — 665 32.5 2.5 — — 7 70 29 1 — —

TABLE 6 Test High Low High Temper- Temper- Temperature ature atureThermal & High 100° C. −30° C. Cycle¹ humidity² for for Solder & Initial500 360 720 1000 1000 connector Pull Z cycles hours hours hours hoursSolder 5 155.82 223.63 134.78 160.83 204.45 161.33 (Sn plating) Solder 6168.42 162.45 102.6  182.75 136.78 159.67 (Sn plating) Solder 7 145.4 164.15 136.2  151.5  103.4  147.78 (Sn plating) Solder 7 226.63 213.05242.95 218.13 219.65 236.95 (Ni plating) Solder 1 188.06 186.53 142.35 94.76 196.25 (Sn plating) Solder 1 204.11 210.57 219.4  209.75 204.73(Ni plating) Solder 2 175.76 166.23 163.48 100.8  197.83 (Sn plating)Solder 2 214.71 211.50 207.6  199.97 217.3  (Ni plating) Solder 3 189.7 166.67 157.00 102.64 221.43 (Sn plating) Solder 3 203.54 222.25 203.35190.5  230.58 (Ni plating) Solder 4 180.6  177.32 151.27 111.3  231.43(Sn plating) Solder 4 215.1  190.05 194.60 192.1  207.8  (Ni plating)¹−30° C. 29 min to 20° C. 1 min to 80° C. 29 min to 20° C. 1 min ²80°C., 95% relative humidity

TABLE 7 Test Corrosion Resistance (immersing for 2 h) Solder Gas Win-and Oil/ dow Con- 0.1N 0.1N Gaso- Diesel Kero- Engine washer nectorH₂SO₄ NaOH line Fuel sene Coolant liquid Solder 159.92 204.35 176.22161.27 164.38 157.75 159.62 5 (Sn Plating) Solder 182.58 189.13 167.2 164.7  171.87 168.5  190.89 6 (Sn Plating) Solder 171.02 157.83 156.95138.88 165.07 150.62 138.98 7 (Sn Plating) Solder 203.42 182.95 215.78223.48 193.78 236.75 211.80 7 (Ni Plating)

1-24. (canceled)
 25. A glazing comprising at least one ply of glasshaving an electrically conductive component on at least one surface, andan electrical connector electrically connected to the electricallyconductive component through a soldered joint, the solder of the jointhaving a composition comprising 0.5 wt % or more indium, wherein theelectrical connector comprises a nickel plated contact for contactingthe solder.
 26. The glazing as claimed in claim 25, wherein the solderhas a composition comprising 0.01 wt % or more Ni.
 27. The glazing asclaimed in claim 25, wherein the solder has a composition comprising0.01 wt % to 5 wt % Ni.
 28. The glazing as claimed in claim 25, whereinthe solder has a composition comprising 0.05 wt % to 5 wt % Ni.
 29. Theglazing as claimed in claim 25, wherein the solder has a compositioncomprising 0.08 to 0.2 wt % Ni.
 30. The glazing as claimed in claim 25,wherein the solder has a composition comprising less than 0.1 wt % Pb.31. The glazing as claimed in claim 25, wherein the solder has acomposition comprising 0.5 wt % or more tin and/or 0.5 wt % or moresilver.
 32. The glazing as claimed in claim 25, wherein the solder has acomposition comprising: 5 to 75 wt % In, to 94 wt % Sn, and 0.1 to 5 wt% Ag.
 33. The glazing as claimed in claim 25, wherein the solder has acomposition comprising 20 to 75 wt % In.
 34. The glazing as claimed inclaim 25, wherein the solder has a composition comprising 60 to 75 wt %In.
 35. The glazing as claimed in claim 25, wherein the solder has acomposition comprising 20 to 60 wt % Sn.
 36. The glazing as claimed inclaim 25, wherein the solder has a composition comprising 0.1 to 5 wt %Cu.
 37. The glazing as claimed in claim 25, wherein the solder has acomposition comprising 0.1 wt % to 2 wt % Cu.
 38. A solder having acomposition comprising: 14 to 75 wt % In, 14 to 75 wt % Sn, 0.1 to 5 wt% Ag, 0.01 to 5 wt % Ni, and less than 0.1 wt % Pb.
 39. The solder asclaimed in claim 38, comprising 20 to 75 wt % In.
 40. The solder asclaimed in claim 39, comprising 60 to 75 wt % In.
 41. The solder asclaimed in claim 38, comprising 20 to 60 wt % Sn.
 42. The solder asclaimed in claim 41, comprising 27 to 32 wt % Sn.
 43. The solder asclaimed in claim 38, comprising 0.08 to 0.2 wt % Ni.
 44. The solder asclaimed in claim 38, comprising 0.1 to 5 wt % Cu.
 45. The solder asclaimed claim 38, comprising 0.8 to 1.2 wt % Ag.
 46. A method ofsoldering an electrical connector to an electrically conductivecomponent on the surface of a ply of glass utilizing a solder as definedin claim
 38. 47. A glazing comprising, at least one ply of glass havingan electrically conductive component on at least one surface, and anelectrical connector soldered to the electrically conductive component,characterised in that the solder has a composition comprising: 14 to 75wt % In, 14 to 75 wt % Sn, 0.1 to 5 wt % Ag, and 0.01 to 5 wt % Ni,preferably 0.06 to 5 wt % Ni.
 48. The glazing as claimed in claim 47,wherein the electrical connector comprises a nickel plated contact forcontacting the solder.
 49. The glazing as claimed in claim 25, whereinthe electrically conductive component comprises electrically conductivesilver-containing ink.
 50. An electrical connector for electricalconnection to an electrically conductive component on the surface of aply of glass through a soldered joint, the solder of the joint having acomposition comprising 0.5 wt % or more indium, and wherein theelectrical connector comprises a nickel plated contact for contactingthe solder.